The evolution of mobile inert gas systems in the tanker trade

Explosions on oil-carrying ships are as old as the tanker trade itself. Inert gas was used with success on vessels as early as 1933 (Sun Oil US). An extra benefit in those early years was that the depletion of oxygen in cargo tanks led to less corrosion of the steel. Strangely, the Second World War saw no significant increase in the use of inert gas; although the US Navy inerted its aircraft carriers with mitrogen (the Japanese did not) most of the tanker fleet was left un-inerted.

In 1956 the Suez Crisis triggered the demand for much larger tankers to carry crude oil from the Middle East to refineries worldwide. But the increasing size of vessels had a downside that would be made horrifically clear. The 1958 Stanvac Japan (26,492 dwt) is well remembered. The vessel was en-route from Bombay to Bandar Mashur in ballast, and in order to load crude again the vessel would probably have been washing out the tanks when it exploded 160 miles south west of Karachi. In this inferno nearly the whole deck opened up like a sardine can: the mid-ship wheelhouse was blown into the sea, with at least 19 casualties.

Aside from Sun Oil and BP, there was little activity on inerting through the 1960s. Some oil majors experimented with inert gas in the late 1950s and early 1960s: although results were well documented, major implementation of inert gas systems (IGS) was not seen until the 1970s. As Jack Devanney of the Center for Tankship Excellence famously once said: “Successful introduction of new technology requires strong direction from management, a hard push at the superintendent level, and commitment by the crews. If any of these are lacking, the whole thing falls apart as soon as the first problem is encountered”.

From 1961 to 1969, numerous lives and ships were lost to explosions and fires where IGS probably would have helped. The 1960s brought bigger and bigger ships. Until then the largest tanker had been 100,000 dwt - but this ceiling was soon breached and vessels with more than double that deadweight were launched from shipyards. Prior to this, the common name for vessels over 50,000 dwt was ‘Supertanker’ so new type names had to be made. The magic word was abbreviation: the world saw the birth of the first VLCCs. Soon though three of those vessels suffered enormous cargo tank explosions while tank cleaning after the cargo was delivered. All of these incidents happened within a period of three weeks in December 1969.

In 1974 the United States Coast Guard began requiring inerting on post-1974 crude carriers over 100,000 dwt trading to the US. Owners who recognised the importance of worldwide trading flexibility started to order their VLCCs with inert gas systems. Despite this legislation, cargo tank explosions (on non-inert vessels) continued into the early 1980s before the underwriters at Lloyd’s stepped in and imposed a surcharge of 0.1 per cent per year on VLCCs not equipped with IGS.

The worst incident was probably the Betelgeuse/Whiddy Island (Bantry Bay, Ireland) disaster in 1979. The worldwide television coverage caused a massive move towards a new safety culture in the business. A few years later, war broke out in the Persian Gulf: there were at least 346 attacks on tankers in the Gulf in six years. In 286 of the 346 attacks, though, the vessels were repaired and brought back on the market. IMO set new rules requiring IGS on all new oil tankers above 20,000 dwt (chemical tankers were exempted) delivered after May 1982.

In 1980, two ex-mariners founded a tanker service company in Rotterdam. They started building hydraulic powerpacks, pumps and other liquid cargo-handling equipment to meet the needs of stricken vessels. During the Gulf War they worked for salvors and P&I clubs to discharge explosion-riddled tankers with portable pumps. They recognised the need for a mobile inert gas generator (IGG), the Gulf War being incident-rich. They acquired a new Port-inert 1500 from Smitgas and put it to use in 1987.

Soon after a second unit was acquired and put to use on board the ill-fated Nagasaki Spirit in 1992. The Nagasaki Spirit was actually a victory for inerting. M/V Ocean Blessing was boarded by Malacca Straits pirates, and under their command the ship fled the scene at flank speed to the east. Out of control at 21 knots, the vessel hit the 95,987 dwt loaded tanker port side. Various cargo tanks on Nagasaki Spirit were set ablaze and the fire spread to the defenceless Ocean Blessing. The inferno killed 25 crew on Ocean Blessing, along with some pirates. On the inerted Nagasaki Spirit, though, the fire was confined to the port side aft: crew members abandoned ship via a starboard lifeboat, but were murdered by pirates for their valuables. In the following salvage, the vessel’s cargo was successfully transferred with MSP-200 portable submersible pumps from inerted tanks. Since the tanker was disabled, the Portinert 1500 IGG maintained the cargo tanks at under 5 per cent O2.

Another victory for mobile cargo-transfer equipment occurred in 1994, when FPSO Lasmo Riau (in Indonesia) was equipped with massive 8in  hydraulic driven submersible pumps and inert gas from The Netherlands after engineroom failure. In the second half of the decade, most incidents requiring mobile inert gas generators were of the operational type, with service providers stocking these worldwide on a standby basis. M/T Lancer (23,470 dwt) exploded in 1998 on the Parana River in Argentina. Lancer was a chemical tanker carrying a cargo of MEK, MIBK and luboil additives upriver in un-inerted tanks. The vessel had cargo tanks empty off IPA and toluene. Lancer suffered three explosions that fireballed one deck tank with ketone into the sky – it landed several kilometres downriver. Several cargo tanks exploded and two lives were lost. The twenty-first century has seen almost all tanker explosions involving ships less than 20,000 dwt or chemical tankers.

In 2004 MariFlex was formed as a result of the merger of two service providers. The company is now at the forefront of liquid cargo-handling equipment, with 24/7 worldwide services such as offloading/pumping, STS transfers, vapour recovery, tanker/barge inerting, debunkering, and salvage support. MariFlex manufactures fire-fighting equipment, pumps and powerpacks. MariFlex Mobile IGG-2000 & N2-500 (nitrogen) generators are self-contained, extremely compact, lightweight and built according to internationally recognised standards and guidelines.

R M Cogels is the founder, president and owner of the MariFlex Group of Companies